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Smallest prime factor of the concatenation of terms in the n-th row of Pascal's Triangle.
3

%I #6 Mar 29 2015 18:41:21

%S 11,11,11,11,7,43,29,18285670562881,5647,13,11,523,180642383,41,17,7,

%T 71,31,4506133,13,170777,29,1921778735419,11,31,197,13,524243,

%U 1294063654237511187554750201560780429214510015005200300103459729051895935678639157755876077558760678639155189593534597290200300101001500542921451560780475020118755237513654406291

%N Smallest prime factor of the concatenation of terms in the n-th row of Pascal's Triangle.

%e a(4) = 11 is the least prime factor of 14641 = 11^4.

%e a(5) = 7 as 15101051 = 7* 2157293.

%t f[n_] := (Table[ #[[1]], {1}] & /@ FactorInteger[ FromDigits[ Flatten[ Table[ IntegerDigits[ Binomial[n, k]], {k, 0, n}]]], FactorComplete -> False])[[1, 1]]; Table[ f[n], {n, 29}] (* _Robert G. Wilson v_, Dec 02 2004 *)

%Y Cf. A100756.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Nov 23 2004

%E More terms from _Robert G. Wilson v_, Dec 02 2004